Automatic channel layering

ABSTRACT

Deploying multiple access points on multiple wireless communication channels to optimize coverage area. Additional channels provide additional communication capability which multiple AP&#39;s, and their associated stations, can collectively use. An additional set of AP&#39;s can be disposed in the additional communication channel, with multiple communication channels possibly physically intersecting. The system control element collects information from devices in the wireless communication system, and automatically configures which AP is assigned to which communication channel. The system control element determines which AP&#39;s are servicing which physical locations, in response to feedback from AP&#39;s and stations in those locations. The system control element assigns, or re-assigns, AP&#39;s in each physical location, with the effect of optimizing coverage.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is related to U.S. Pat. No. 7,826,426 issued to VaduvurBharghavan et al. and entitled “Seamless Mobility in Wireless Networks,”the entire contents of which are hereby incorporated by reference.

BACKGROUND

In wireless communication using an IEEE 802.11 protocol, wirelessstations connect to a wireless communication system using access points(“AP's”). Each AP services those stations which it is best suited toservice, typically those stations which are nearest or otherwise havebest signal strength, and for which there is little or no interferencewith other access points. If the AP's are spaced too far apart, theremight be regions (“coverage holes”) in which coverage by the system islimited, spotty, or even nonexistent. For example, this can be due todifficulty by stations in finding an access point with adequate signalstrength. On the other hand, if the AP's are spaced too closely, theremight be regions in which the wireless communication system is operatinginefficiently. For example, this can be due to difficulty by accesspoints in communicating without interference.

In a system described in the Incorporated Disclosures, a system controlelement selects, for each station, which AP will communicate with, andservice, that station. Multiple AP's can each communicate with theirassociated stations in the communication system. This has the effectthat multiple AP's can be disposed nearby, even co-located, and canconfigured to operate in the same channel without leaving any coverageholes. However, one problem is that channel capacity is limited byinterference between the set of devices using the same channel.

BRIEF SUMMARY

We provide techniques for deploying multiple access points on multiplewireless communication channels, without leaving any significant areasof limited coverage (sometimes referred to herein as “coverage holes”).

In a wireless communication system organized having multiple channels,we provide an association between AP's and those channels. Theassociation maximizes coverage by AP's servicing stations attempting touse the communication system. This has the effect that each additionalchannel provides additional communication capability which additionalAP's, and their associated stations, can collectively use once thoseadditional AP's are assigned to those additional communication channels.This also has the effect that AP's can be physically close to preventcoverage holes in service, without interfering with each other.

The system control element collects information from devices in thewireless communication system, and automatically configures which AP isassigned to which mobile stations. The system control element determineswhich AP's are servicing which physical locations, in response tofeedback from AP's and stations in those locations. The system controlelement assigns, or re-assigns, AP's in each physical location, with theeffect of achieving maximum coverage. This has one effect that thesystem control element can balance loading on each communication channelby assigning or re-assigning stations to its choice of communicationchannel. The system control element can, from time to time, collect newinformation and assign or re-assign AP's to channels, with the effect ofre-achieving maximum coverage even after conditions change.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a conceptual diagram of a wireless communication system.

FIG. 2 shows a conceptual diagram of a method.

DETAILED DESCRIPTION Terms and Phrases

The following terms and phrases include their most general applicableform. Each is described in a manner that is illustrative, not limiting.

The phrase “access point”, and the term “AP”, and variants thereof,generally refers to any device capable of coupling wireless messagesbetween a wireless station and a wired communication medium. Accesspoints might be coupled directly to a wired medium, such as for examplea LAN or other wired network. Alternatively, access points might becoupled indirectly to a wired medium, such as for example using otheraccess points, wireless repeaters, or otherwise.

In one embodiment, particular access points might be movable in regionsrelated to a wireless communication system. For example and withoutlimitation, the system might direct those particular access points to bemoved to locations where communication is problematic, or to locationssuitable for assisting in determining communication problems or remediestherefor.

The terms “assignment”, “association”, and variants thereof, when usedwith respect to AP's and channels, generally refer to any method orsystem in which those AP's are directed to, or otherwise operate to,communicate using those channels. For example, the system controlelement might assign an AP to a particular channel using a message sentto that AP, or by making an entry in an AP/channel table that the APreviews, or otherwise.

The phrases “wireless communication”, “wireless network”, and variantsthereof, generally refer to any method or system in which data ormessages are sent, received, or maintained, using a wireless medium. Forexample and without limitation, the wireless medium might includeelectromagnetic radiation, such as radio frequencies. In one embodiment,wireless communication is performed using a communication protocolfamily such as IEEE 802.11, or a variant thereof. However, in thecontext of the invention, there is no particular requirement for anysuch limitation.

The phrase “wireless station”, and variants thereof, generally refers toany end-user device capable of communicating using wireless messages ina wireless communication system. For example and without limitation,wireless stations might include cellular phones, laptop computers,netbooks (such as the “iPad”), or other devices. Wireless stations mightbe mobile (and might sometimes be referred to herein as “mobilestations”) or might be stationary.

In one embodiment, particular access points might be directed by awireless communication system to perform as wireless stations,exchanging messages with those access points performing the functionsgenerally associated with access points; in such cases, those particularaccess points performing as wireless stations might be sometimes treatedherein as if they were wireless stations.

Generality of the Description

Technologies shown or suggested by this description should also bethought of in their most general possible form. This includes, withoutlimitation, the following:

The phrases and terms “constantly,” “continually,” “from time to time,”“occasionally,” “periodically” (and similar phrases and terms) generallyindicate any case in which a method or technique, or an apparatus orsystem, operates over a duration of time, including without limitationany case in which that operation occurs only part of that duration oftime. For example and without limitation, these terms would include,without limitation, methods which perform an operation as frequently asfeasible, on a periodic schedule such as once per second or once perday, in response to an alarm or trigger such as a value reaching athreshold, in response to a request or an implication of a request, inresponse to operator intervention, otherwise, and to combinations andconjunctions thereof.

The phrases and terms “methods, physical articles, and systems,”“techniques” (and similar phrases and terms) generally indicate anymaterial suitable for description, including without limitation all suchmaterial within the scope of patentable subject matter, or having everbeen considered within the scope of patentable subject matter, or whichmight colorably be within the scope of patentable subject matter,notwithstanding most recent precedent.

The term “relatively” (and similar phrases and terms) generallyindicates any relationship in which a comparison is possible, includingwithout limitation “relatively less,” “relatively more,” and the like.In the context of the invention, where a measure or value is indicatedto have a relationship “relatively,” that relationship need not beprecise, need not be well-defined, need not be by comparison with anyparticular or specific other measure or value. For example and withoutlimitation, in cases in which a measure or value is “relativelyincreased” or “relatively more,” that comparison need not be withrespect to any known measure or value, but might be with respect to ameasure or value held by that measurement or value at another place ortime.

The term “substantially” (and similar phrases and terms) generallyindicates any case or circumstance in which a determination, measure,value, or otherwise, is equal, equivalent, nearly equal, nearlyequivalent, or approximately, what the measure or value is recited. Theterms “substantially all” and “substantially none” (and similar phrasesand terms) generally indicate any case or circumstance in which all buta relatively minor amount or number (for “substantially all”) or nonebut a relatively minor amount or number (for “substantially none”) havethe stated property. The terms “substantial effect” (and similar phrasesand terms) generally indicate any case or circumstance in which aneffect might be detected or determined.

The phrases “this application,” “this description” (and similar phrasesand terms) generally indicate any material shown or suggested by anyportions of this application, individually or collectively, includingall documents incorporated by reference or to which a claim of prioritycan be made or is made, and include all reasonable conclusions thatmight be drawn by those skilled in the art when this application isreviewed, even if those conclusions would not have been apparent at thetime this application is originally filed.

The invention is not in any way limited to the specifics of anyparticular examples disclosed herein. After reading this application,many other variations are possible which remain within the content,scope and spirit of the invention; these variations would be clear tothose skilled in the art, without undue experiment or new invention.

Figures and Text

FIG. 1

FIG. 1 shows a conceptual diagram of a wireless communication system.

A wireless communication system 100 includes elements shown in the FIG.1, including a set of wireless communication channels 110, one or moreAP's 120, one or more stations 130, and at least one system controlelement 140.

The wireless communication channels 110 each include a physicalcommunication layer, such as for example a physical communication layerused by an IEEE 802.11 protocol or a variant thereof. The physicalcommunication layer provides devices coupled to the system 100 theability to send and receive messages using a wireless substrate, such asfor example using electromagnetic radiation in a radio frequency band.As described herein, there are multiple such channels 110 on whichcommunication might occur separately without substantial interference,which might be separable using distinct CDMA codes, distinctfrequencies, MIMO separation, distinct TDMA time slots, or otherwise.For example, in the 2.4 GHz ISM band used by IEEE 802.11 protocols thereare 3 20-MHz channels, while in the 5 GHz band there are at least 440-MHz channels in most countries, and up to 12 40-MHz channels in somecountries.

Each wireless communication channel 110 is conceptually represented inthe figure as a separate network, as if each communication channel 110were independently accessible by each AP 120. In one embodiment, eachcommunication channel 110 has an independent FDMA frequency, such asdescribed above with respect to the 2.4 GHz band and the 5 GHz band usedby IEEE 802.11 protocols, and each AP 120 includes a radio capable ofbeing tuned to either (1) any one of those FDMA frequencies in the 2.4GHz band, or (2) any one of those FDMA frequencies in the 5 GHz band.This has the effect that each AP 120 with a radio tunable in the 2.4 GHzband can be assigned, if desired, to any one of the communicationchannels 110 in the 2.4 GHz band, and each AP 120 with a radio tunablein the 5 GHz band can be assigned, if desired, to any one of thecommunication channels 110 in the 5 GHz band.

This also has the effect that multiple AP's 120 can communicateconcurrently on distinct communication channels 110 withoutinterference. For example, if two AP's 120 are each transmitting orlistening on distinct communication channels 110 (such as for example,distinct frequencies), interference between those two AP's 120 should besubstantially zero, allowing those two AP's 120 to each act as if theother AP 120 was not present. Thus, if two or more AP's 120 aresubstantially co-located, those AP's 120 might be assigned to distinctcommunication channels 110 so as to allow them to service stationsconcurrently without interference.

If an AP 120 has more than one radio, each radio can be assigned to aseparate communication channel 110. In one embodiment, this might betreated as if the AP 120 with more than one radio emulates a pluralityof co-located AP's 120, or might be alternatively treated as if the AP120 with more than one radio is concurrently assigned to a plurality ofcommunication channels 110. Similarly, it might occur that a pluralityof AP's 120, collectively having more than one radio, or otherwisecapable of collectively operating on more than one communication channel110, might cooperate so as to collectively emulate a plurality ofco-located AP's 120, or might cooperate so as to collectively act like asingle AP 120 which is concurrently assigned to more than onecommunication channel 110.

In one embodiment, an AP 120 might have multiple radios, each of whichis configured to operate on a particular frequency band. For example,one particular frequency band could be either the 2.4 Ghz band or the 5Ghz band described above, or possibly some additional or other frequencyband that might be envisaged in the future. In this example, the AP 120with multiple radios can be considered as if it included more than onecollocated AP 120, each of which with a single radio capable ofoperating on its own, separately configured, frequency band.Subsequently, distinct sets of AP's 120 are formed in every frequencyband such that the AP's 120 from each of those distinct sets operate onthe same frequency band. The method described herein can then be appliedseparately on each of the sets of AP's 120, with the effect of arrivingat an optimal assignment of radios to channels within each particularfrequency band.

While this application primarily describes systems in which each AP 120has only a single radio and is therefore capable of communication ononly a single communication channel 110 at once, in the context of theinvention, there is no particular requirement for any such limitation.

While this application primarily describes techniques in which each AP120 is assigned to a single communication channel 110 (or a singlecommunication channel 110 for each of its radios), in the context of theinvention, there is no particular reason for any such limitation. Forexample, one or more AP's 120 might be directed to switch between oramong two or more communication channels 110, with the effect that thoseAP's 120 might listen on more than one communication channel 110,although not simultaneously, and with the effect that those AP's 120might transmit on more than one communication channel 110, although notsimultaneously. AP's 120 directed to act in that manner might switchcommunication channels 110 periodically, or from time to time inresponse to one or more stimuli.

However, it might be the case that not all of the communication channels110 can be reached by all of the AP's 120. For example, as describedabove, in one embodiment it occurs that some AP's 120 are only able toreach the communication channels 110 in the 2.4 GHz band, and lackability to reach the communication channels 110 in the 5 GHz band, whileother AP's 120 are only able to reach the communication channels 110 inthe 5 GHz band, and lack ability to reach the communication channels 110in the 2.4 GHz band. The control element 140 would assign those AP's 120only to communication channels 110 they are actually able to reach. Forexample, the control element 140 might attempt to determine a coveringset for the wireless communication system 100 by first restricting itsattention to AP's 120 to a particular frequency band.

While this application primarily describes systems in which each AP 120has is capable of communication on all the frequencies of a particularfrequency band (e.g., the 2.4 GHz band or the 5 GHz band), in thecontext of the invention, there is no particular requirement for anysuch limitation. As described below, the control element 140 isgenerally able to assign AP's 120 to any communication channel 110, andwill generally make those assignments in response to physical proximityand other coverage factors.

The control element 140 determines, from time to time for each station130, which AP 120 will communicate with that station 130 and service it.This has the effect that each station 130 sees each channel 110 as asingle communication system, through which the station 130 might moveabout without having to attend to handoffs between AP's 120. Even if thestation 130 does not physically move, the control element 140 canre-assign the station 130 to a different AP 120 where that might provideimproved service to the station 130. For a first example, inelectromagnetic conditions might change, such as due to increased ordecreased amounts of interference from other devices. For a secondexample, the number of stations 130, or the demand placed on thecommunication system by stations 130, in the vicinity of AP's 120 mightchange over time, to which the control element 140 can respond byre-associating AP's 120 with stations 130, such as possibly to balancethe load on AP's 120 to amounts commensurate with what those AP's 120can handle.

Each AP 120 reports the RSSI value it has for each station 130 it canhear, even if that station 130 is not then currently assigned to that AP120. This has the effect that the control element 140 can determinewhether a station 130 would be better off re-assigned to a new AP 120.In one embodiment, the control element 140 makes the determination ofwhether to re-assign any particular station 130 in response to the RSSIvalue for each nearby AP 120, as well as in response to a measure ofloading for each of those nearby AP's 120. This has the effect that thecontrol element 140 can assign stations 130 to the AP 120 best able toservice them, where “best able to service” can include factors such ashow good the communication path they have with that AP 120 and whetherthat AP 120 has sufficient resources to service them.

While this application primarily describes a communication system 100 inwhich AP's 120 report their RSSI values, in the context of theinvention, there is no particular requirement for any such limitation.

For a first example, AP's 120 might also report additional informationto the control element 140, possibly including amount of traffic at ornear each AP 120, number of stations at or near each AP 120, activity byeach station 130, and other information. The control element 140 mightuse this additional information to determine which AP's 120 are likelyto become overloaded, or which AP's 120 are likely to involvereassignment from one communication channel 110 to another to effectload-balancing. Load balancing might be desirable either to maintain arelatively even load across communication channels 110, or to maintain arelatively even load across AP's 120, or to maintain a relatively evendegree of service to stations 130, or otherwise.

For a second example, the communication system 100 might includeadditional sensing devices 121 whose purpose is to sense informationabout operation of the communication system 100 and report thatinformation to the control element 140. Those additional sensing devices121 might report similar information as described with respect to AP's120. Additional sensing devices 121 might be relatively simple devicesin comparison with AP's 120, as they need only listen to traffic theycan hear and report statistics regarding that traffic to the controlelement 140, without needing to actually service any stations 130.

For a third example, the control element 140 might query stations 130for RSSI values those stations 130 report with respect to their assignedAP's 120, and might obtain similar additional information as describedwith respect to AP's 120. The control element 140 might require allstations 130 to report RSSI values or additional information, or mightselect only a subset of stations 130 to make such reports, or mightdistinguish between stations 130 which report more information andstations 130 which report less information. Similarly, the controlelement 140 might direct some stations 130 to report to their servicingAP's 120, might direct some stations 130 to report to non-servicing AP's120, might direct some stations 130 to report to additional sensingdevices 121 as described above, or otherwise.

Each AP 120 has an associated set of stations 130 serviced by that AP120, for which the RSSI value is relatively good, that is, the abilityof that AP 120 to communicate with the stations 130 it is assigned toservice is relatively good compared with other stations 130. Whilestations 130 are often assigned to AP's 120 in response to theirdistance from that AP 120, in the context of the invention, there is noparticular reason for any such limitation. For example, it mightcommonly occur that walls and other obstacles would alter the ability ofan AP 120 to hear stations 130 that are physically proximate, with theeffect that the group of stations 130 assigned to a particular AP 120might have an unusual boundary at or near an obstacle.

The control element 140 receives status messages from each AP 120, thosestatus messages reporting at least an RSSI (received signal strengthindicator) value for each station 130 that AP 120 can hear. The controlelement 140 interprets those status messages, or has those statusmessages interpreted for it by an auxiliary device, and maintains thoseRSSI values in an data structure 141. The data structure 141 might bemaintained either at the control element 140, or at another deviceaccessible by the control element 140.

FIG. 2

FIG. 2 shows a conceptual diagram of a method.

A method 200 includes a set of flow points and labels and shown in thefigure, including at least: a flow point 200A indicating a beginning ofthe method, a flow point 210 that the method is ready to assign AP's 120to a first channel 110, a flow point 220 indicating that the method isready to assign AP's 120 to a next channel 110, and a flow point 200Bindicating an end of the method.

Beginning of Method

The flow point 200A indicates a beginning of the method 200. In oneembodiment, the method 200 is triggered from time to time, such as (1)whenever the control element 140 determines that the wirelesscommunication system is not best using its channel capacity, (2)whenever a sufficient time passes, or otherwise.

At a step 201, the method 200 initializes its assignment of all AP's 120to a 1st communication channel 110, and initializes a “goodness-index”value to zero for each AP 120. The “goodness-index” value generallyindicates whether the AP 120 is properly assigned to the communicationchannel 110 to which it is already assigned.

As described herein, the method 200 begins with all AP's 120 generallyassigned to the same communication channel 110. However, in the contextof the invention, there is no particular requirement for any suchlimitation. For example, as noted above, it might occur that some AP's120 are limited to only a particular subset of communication channels110. It might be advantageous for the control element 140 to begin themethod 200 with those AP's 120 whose operating capability is limited tostart assigned to one of the limited communication channels 110, such asfor example, a limited set of operating frequencies, which they arecapable of using.

At a step 202, the method 200 collects a set of RSSI values reported byeach AP 120 for each station 130 it can hear. The collected RSSI valuesare maintained by the method 200 in a data structure 141. In oneembodiment, the data structure 141 might be maintained at the controlelement 140, such as in memory or mass storage coupled to a processorperforming the operations associated in this application with thecontrol element 140. In alternative embodiments, the data structure 140might be maintained external to the control element 140, but stillaccessible to the control element 140, such as in a network attachedstorage element coupled to the control element 140, or such as in aInternet-accessible database server with the control element 140 coupledto the Internet.

In one embodiment, the AP's 120 each send one or more messages to thecontrol element 140 reporting the RSSI values they each have to report.In embodiments in which the data structure 141 is maintained at thecontrol element 140, the control element 140 records information fromthose messages in the data structure 141. In alternative embodiments inwhich the data structure 141 is not maintained physically at the controlelement 140, but is accessible by the control element 140, the AP's 120might send messages to a device where the data structure 141 ismaintained, or might modify the data structure 141 themselves to addtheir information. Either way, the data structure 141 maintains the RSSIvalues reported by each AP 120.

The method 200 proceeds from the flow point 210.

Covering Subset

A flow point 210 indicates that the method 200 is ready to assign AP's120 to a first channel 110.

As described below, the method 200 determines a subset of the AP's 120that are sufficient to provide coverage, on the first channel 110, to asmany stations 130 as possible. Once this subset of AP's 120 isdetermined, the method 200 can assign the remaining AP's 120 to one ormore additional channels 110.

At a step 211, for each station 130, the method 200 finds the “best” AP120 for that station 130, defined for this step as the AP 120 which hasthe best (that is, highest) RSSI value for that station 130. Havingfound the best AP 130 for that station 130, the method 200 finds asecond-best AP 120 for that station 130, and computes a differencebetween the best RSSI value and the next best RSSI value. The method 200assigns the RSSI difference, that is, the difference between the bestRSSI value and the next best RSSI value, to the best AP 120 for thatstation 130.

The method 200 performs this step for each station 130. This has theeffect of determining, for each station 130, its best AP 120 and theRSSI difference for that best AP 120. This also has the effect ofdetermining, for each AP 120, its RSSI difference for each station 130.

At a step 212, for each AP 120, the method 200 finds the highest valueof its RSSI difference over all stations 130, that is, the highest RSSIdifference found when its RSSI value for all stations 130 are accountedfor. This has the result that, if a particular AP 120 is the best AP 120for only one particular station 130, its highest RSSI difference will beits RSSI difference for that one station. If a particular AP 120 is thebest AP 120 for two or more stations 130, its highest RSSI differencewill be the maximum of its RSSI differences for those two or morestations 130.

For each AP 120, the method 200 records its highest RSSI difference as anew goodness-index for that AP 120. Thus, the recorded goodness-indexfor an AP 120 will be the best RSSI difference the method 200 can find,for all stations 130 reported for that AP 120. To avoid the possibilityof spurious values being reported, which might occur in response tonoise or other fluctuations in RSSI values, the method 200 only recordsa new value for an AP's goodness-index when it obtains two consecutivenew values for goodness-index higher than the most recentgoodness-index, and when so, records the lower of those two consecutivenew values as the AP's new goodness-index.

At a step 213, the method 200 marks all AP's 120 whose goodness-index isat least a threshold value of 3 dB as being assignable to the currentchannel 110. While this application primarily describes a method 200which uses 3 dB as a threshold value for assigning AP's 120 to thecurrent channel 110, in the context of the invention, there is noparticular requirement for any such limitation. For a first example, themethod 200 might use 2 dB or 4 dB for the threshold value, or any otherselected value. For a second example, the method 200 might select thethreshold value in response to a number of available communicationchannels 110, in response to a best RSSI difference among all AP's 120,in response to a number of AP's 120, or otherwise.

In one embodiment, when the method 200 assigns an AP 120 to a particularcommunication channel 110, the control element 140 records anassociation between that communication channel 110 and that AP 120 in adata structure, and sends a message to that AP 120 directing that AP 120to use that communication channel 110. The data structure in which thatassociation is recorded can be the same data structure 141, oralternatively, another data structure. In alternative embodiments, theAP's 120 can review that data structure for themselves, with anyparticular requirement that the control element 140 send messages tothose AP's 120.

When an AP 120 is assigned to a particular communication channel 110, itgenerally listens for stations 130 desiring to receive or send messagesusing that communication channel 110, and sends its messages using thatcommunication channel 110. However, the AP 120 might also listen tomessages on a secondary communication channel 110 for other reasons. Forexample, the AP might listen on a secondary communication channel 110for “emergency” or otherwise high-priority messages, or might listen ona secondary communication channel 110 for messages from other AP's orfrom the control element, or might listen on a secondary communicationchannel 110 for collecting information about traffic in thecommunication system 100, or otherwise.

At a step 214, the method 200 finds the one AP 120 with the lowestgoodness-index and assigns that AP 120 to the next channel 110. If thereis more than one AP 120 with that lowest goodness-index value, themethod 200 selects one of them at random with equal probability. Whilethis application primarily describes a method 200 which selects one ofthose AP's 120 at random, in the context of the invention, there is noparticular requirement for any such limitation. For example, the method200 might select one of those AP's 120 in response to another factor,such as a proximity to other AP's 120, or proximity to stations 130, orotherwise.

At a step 215, the method determines if there are any remaining AP's 120whose goodness-index is less than the threshold value of 3 dB. If so,the method 200 returns to the flow point 210, and repeats the steps fromthe flow point 210 to this point, that is, the steps 211, 212, 213, and214, until there are no more such AP's 120. When this occurs, the method200 has completed assigning AP's 120 to the current channel 110, andmoves to the next channel 110.

When the step 215 is finished, the subset of AP's 120 assigned to thecurrent channel 110 include AP's which can operate on the currentchannel 110, and which provide substantially as much coverage as theentire original set of AP's 120. With respect to the current channel110, those AP's 120 remaining for the next channel 110 are substantiallyredundant. The method 200 repeats the same technique for each nextchannel 110 in turn, until all AP's 120 have been assigned to a channel110.

The method 200 proceeds from the flow point 220.

Next Channel

A flow point 220 indicates that the method 200 is ready to assign AP's120 to a next channel 110.

At a step 221, with respect to the AP's 120 that were not alreadyassigned to the first channel 110, the method 200 repeats the stepsbetween the flow points 210 and 220, that is, the steps 211, 212, 213,214, and 215, for each channel 110 in turn.

Thus, if there are 4 available channels 110, the method 200 performsthose steps for the first channel, selecting a first subset of AP's 120to assign to the first channel and a remaining group of AP's 120 whichcan be assigned otherwise. The method 200 repeats those steps for thesecond channel, selecting a second subset of AP's 120 to assign to thesecond channel and a remaining group of AP's 120 which can be assignedotherwise, and so on, until all remaining AP's 120 are assigned to thelast available channel 110. The latter condition occurs when there areno AP's 120 in the current group being considered which are redundantand thus which can be moved to a next channel 110.

Redundant AP's

If the method 200 continues to have redundant AP's 120 but has no morechannels 110 to which to move those redundant AP's 120, the method 200can assign those redundant AP's 120 to support the AP's already assignedto a channel 110. For example, the method 200 might (1) assign thoseredundant AP's 120 to a channel 110 which could use backup in the eventone of its AP's 120 fails to operate, (2) just leave those redundantAP's 120 on the channels 110 where they are already located, or (3)retry the channel 110 assignments with a different requirement, such as2 dB instead of 3 dB.

After reading this application, those skilled in the art would noticethat the subset of AP's 120 assigned to the first channel 110 provide asmuch coverage as the entire original set of AP's 120, and that the AP's120 which remain for assignment to later channels 110 might not have asgood coverage, they can still provide extended capacity by use of thoselater channels 110. Similarly, for each channel 110, the subset of AP's120 actually assigned to that channel 110 provide as much coverage asthe entire group of AP's 120 remaining for assignment to that channel110 or later channels 110.

The method 200 proceeds from the flow point 200B.

End of Method

A flow point 200B indicates an end of the method 200. In one embodiment,the method 200 is repeated, from time to time, from the beginning at theflow point 200A.

We claim:
 1. A method in a device coupled to a wireless communicationsystem having more than one communication channel and having a set ofaccess points capable of providing service to stations, the methodcomprising: defining a data structure representing a set of saidcommunication channels and a group of access points from which to selecta covering subset of access points, altering said data structure to letthat selectable set equal all access points in said communicationsystem, and altering said data structure to identify a current channel;collecting information from devices coupled to that system, saidinformation sufficient to determine a capability of each of those accesspoints of providing service to stations; determining, for a first accesspoint, a relative coverage capability compared to one or more secondsaid access points; in response to said relative coverage capability,selecting said covering subset from that group of access points, theselected covering subset being sufficient to provide coverage tostations in said communication system as good as said group of accesspoints; sending one or more messages to said access points in saidcovering subset, assigning them to said current channel; altering saiddata structure to let that selectable set equal those access pointsremaining after removing said covering subset, and to identify a nextchannel; and repeating said steps of selecting, sending, and alteringuntil either each access point has been assigned to one of saidchannels, or each channel has had an one or more access points assignedthereto.
 2. A non-transitory computer-readable medium storing a computerprogram product to perform a method in a computing device coupled to awireless communication system having more than one communication channeland having a set of access points capable of providing service tostations, the method comprising: defining a data structure representinga set of said communication channels and a group of access points fromwhich to select a covering subset of access points, altering said datastructure to let that selectable set equal all access points in saidcommunication system, and altering said data structure to identify acurrent channel; collecting information from devices coupled to thatsystem, said information sufficient to determine a capability of each ofthose access points of providing service to stations; determining, for afirst access point, a relative coverage capability compared to one ormore second said access points; in response to said relative coveragecapability, electing said covering subset from that group of accesspoints, the selected covering subset being sufficient to providecoverage to stations in said communication system as good as said groupof access points; sending one or more messages to said access points insaid covering subset, assigning them to said current channel; alteringsaid data structure to let that selectable set equal those access pointsremaining after removing said covering subset, and to identify a nextchannel; and repeating said steps of selecting, sending, and alteringuntil either each access point has been assigned to one of saidchannels, or each channel has had an one or more access points assignedthereto.